Alloc glyph image correctly for SkMask::k3D_Format.

Remove the no longer used outside Skia SK_SUPPORT_LEGACY_EMBOSSMASKFILTER
define, and either delete the code it guards or update it to use the new
emboss mask filter factory.

Re-enable the code to test the emboss mask filter.

Add a test to ensure that embossed text is drawn correctly, as before
glyphs did not allocate the proper amount of memory for the k3D_Format
which the emboss mask filter produces.

Fixes SkEmbossMask::Emboss to write the whole of the mul and add planes
to avoid pixel differences and MemorySanitizer errors.

Update the GPU to understand the k3D_Format and use just the alpha
plane, ignoring the mul and add plane which it currently cannot support.

Change-Id: Icac1a3f37d6e8c6be3151df570f5e14111e18585
Reviewed-on: https://skia-review.googlesource.com/70260
Reviewed-by: Herb Derby <herb@google.com>
Reviewed-on: https://skia-review.googlesource.com/70962
Commit-Queue: Ben Wagner <bungeman@google.com>
9 files changed